Extended Data Fig. 1: Similar total amounts of aequorin in the wild-type and hpca1 seedlings.

a, The Arabidopsis wild-type and hpca1 seedlings expressing aequorin (used in Fig. 1a) were treated with a solution containing 0.9 M CaCl₂ and 10% (v/v) ethanol (aequorin discharge), and the total amount of remaining aequorin luminescence was imaged. Images are representative of more than 100 separate experiments. The relative [Ca²⁺]_i is scaled by a pseudo-colour bar. b, Quantification of total amount of aequorin luminescence from as in a. Data are mean ± s.d.; n = 12 pools (20 seedlings per pool). P = 0.806, two-sided t-test. About 10 years before Price et al. made the initial observation of eH₂O₂-induced [Ca²⁺]_i increases in plant cells in 1994¹⁷, Hyslop et al. investigated the effects of eH₂O₂ on [Ca²⁺]_i in mouse macrophage cells using the intracellular fluorescent Ca²⁺ indicator Quin2, and detected [Ca²⁺]_i increases in response to eH₂O₂ treatment⁷⁴. Note that, Quin2 was the predecessor of Fura-2, the most important Ca²⁺ indicator⁷⁵.

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